Titration is a well known method for determinating a concentration of a constituent of a solution or for determining a characteristic of a solution. In traditional titration acidity or alkalinity is determined by adding an acid or base to a solution containing an indicator. When the pH reaches a particular value, the color of the indicator changes. For example, a common indicator is phenolpthalein which is colorless in acidic solutions, but is red in solutions having a pH exceeding nine. Other well known indicators that change colors at particular pH's are: methyl orange xylene cyanol, methyl red, litmus, and bromophenol blue. Other indicators are available for responding to the presence of particular ions in solution. For example, permanganate ions respond to the presence of iron or nitrite ions in solution. A characteristic of a solution containing an indicator may be determined from the quantity of a titrant of known concentration (e.g., acidity) added to the solution to bring about a change in indicator color.
Titrations are conveniently carried out in a laboratory environment with relatively inexpensive apparatus since conditions can be easily controlled. However, in manufacturing operations where conditions are not so easily controlled, employment of titration to test or analyze and thereby control the characteristics of various chemical baths is more difficult and expensive. In many situations, analytical techniques other than titration are employed to monitor characteristics of solutions, such as plating baths, including spectroscopy techniques that require expensive and complex apparatus.
In manufacturing operations, titration can be an effective means of determining when a chemical bath requires replenishment or addition of make-up chemicals to maintain characteristics within a desired range. Yet, employment of titration as a process control technique has been retarded because available apparatus is complex making it difficult to maintain and expensive to purchase and install. Accordingly, there is a need for an automated, inexpensive titration apparatus for use in process control.